Fix memory leaks.

Fix memory leaks.

Original commit message from CVS:
* ext/flac/gstflactag.c: (gst_flac_tag_init):
* gst/interleave/deinterleave.c: (deinterleave_init),
(deinterleave_sink_link):
* gst/interleave/interleave.c: (interleave_init):
* gst/median/gstmedian.c: (gst_median_init):
* gst/oldcore/gstmultifilesrc.c: (gst_multifilesrc_init):
Fix memory leaks.
* tests/check/elements/id3demux.c: (pad_added_cb):
Remove unused variable.